U.S. Pat. No. 4,412,947 to Cioca discloses a collagen sponge and a method for preparing it; as disclosed in Example II, the sponge may be in the form of a sheet and is suitable for use as a wound dressing, burn dressing, hemostatic sheet or the like. U.S. Pat. No. 3,632,361 to Battista discloses a water-insoluble, highly absorbent body or mat of collagen formed by freeze-drying, in a mold, a dispersion of collagen in aqueous medium. U.S. Pat. No. 4,600,533 to Chu, entitled "Collagen Membranes for Medical Use," discloses a gel of collagen which is compressed to a mat, then dried, or a gel which is centrifuged, then dried. No freeze-drying is used in the Chu process.
Additional prior art collagen products are disclosed in a number of additional references, including Khosla, A.S. et al., "Mechanical Response of Reconstituted, Freeze-Dried Collagen Under Compressive Loads," J. Biomechanics, Vol. 17, No. 7 (1984) pp. 491499, and a number of United States patents. These U.S. patents include U.S. Pat. No. 4,279,812, U.S. Pat. No. 4,295,894, U.S. Pat. No. 4,327,195, U.S. Pat. No. 4,374,121, U.S. Pat. No. 4,412,947, and U.S. Pat. No. 4,515,637 all to Cioca, British Patent No. 347,582 to Cioca, U.S. Pat. No. 4,597,762 to Walter et al. and U.S. Pat. No. 4,389,487 to Ries. The aggregate prior art as cited discloses collagen articles which may form pelts, may include polyurethanes and other materials, may be prepared either into wooly materials or prostheses, i.e., breast implants, etc., and generally may provide a specialized function for a given medical or surgical application.
Notwithstanding the variety of materials taught by the prior art, the references identified above do not teach or suggest the solution to the ubiquitous problem of high porosity and excessive resilience in collagen and collagen-containing sheet materials. Accordingly, a need remains for a wound dressing or hemostatic sheet material, prepared primarily of collagen, which has improved mechanical stability and is adequately dense and sufficiently conformable for topical medical/surgical utility.